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SPN 3216 FMI 2

Aftertreatment 1 Intake NOx — Data erratic, intermittent, or incorrect.
The signal jumps around, drops in and out, or disagrees with other information the controller has.

What the SPN covers: NOx sensor reading in the exhaust before the SCR catalyst (engine-out NOx). More on SPN 3216.

What FMI 2 usually points to: Loose or corroded connectors, chafed wiring, a failing sensor, or two redundant sensors that do not agree. More on FMI 2.

Severity

MEDIUM — fix soon

Can lead to SCR efficiency codes and inducement derates if not repaired.

Likely causes

  1. Failed NOx sensor (common)
  2. Sensor not reaching operating temperature
  3. Exhaust leak near the sensor
  4. Network or power fault to the sensor module

Checks & fixes (easiest first)

  1. Check for exhaust leaks upstream of the sensor
  2. Check sensor power/ground and CAN wiring
  3. Compare inlet and outlet NOx readings
  4. Replace sensor per OEM test results

FAQ

What does SPN 3216 FMI 2 mean?

Aftertreatment 1 Intake NOx — data erratic, intermittent, or incorrect. The signal jumps around, drops in and out, or disagrees with other information the controller has.

Is SPN 3216 FMI 2 serious?

Can lead to SCR efficiency codes and inducement derates if not repaired.

What should I check first for SPN 3216 FMI 2?

Check for exhaust leaks upstream of the sensor; Check sensor power/ground and CAN wiring; Compare inlet and outlet NOx readings.